The features of the present invention are particularly useful as applied to the construction of incandescent lamps employed in automobiles, such as the dual-filament lamps employed in tail light assemblies.
One well known example of existing lamps of this type generally employ a type S-8 glass bulb cemented in a brass, double contact bayonet base. Although used for a number of years, such bases pose a number of disadvantages. For example, anyone who has replaced such a lamp in their automobile will appreciate the great difficulty experienced in position-referencing the base to insure the proper lamp-to-socket orientation. The base is usually cylindrical in shape and the only orientation reference means are small indexing pins at the sides thereof. This referencing problem also holds true for automatic insertion of the lamp into the socket during production thereof. Further, the lamp to base construction for dual filament lamps of this type requires three soldering points for electrical connections (the two lead-in wires serving as the common connection are twisted and soldered to the sidewall of the base, while the other two wires are respectively soldered to the twin contact nodes at the bottom of the base). This leads to corrosion or other contact degradation problems caused by soldering fluxes. Finally, the bayonet base lamp requires a somewhat complicated and relatively expensive socket design.
One attempted solution to the several aforementioned problems inherent in brass base lamps is defined in U.S. Pat. No. 4,028,577 (P. E. Gates et al), said patent assigned to the same assignee as the instant invention and being a continuation-in-part of U.S. Pat. No. 3,979,627 (S. J. Leadvaro et al). In U.S. Pat. No. 4,028,577, there is described an electric lamp having a sealed end containing therein (or extending therefrom) a reentrant glass stem sealed about its periphery to the glass bulb. This end is positiond within a plastic base having a cylindrical body portion (for housing the somewhat cylindrical-shaped sealed end) and adjacent wedge portion. While this concept has proven advantageous in several ways over the aforementioned brass base lamps, it is necessary to provide additional features, steps, etc. in order to satisfactorily produce and utilize this arrangement. For example, it is necessary to position the extending top segment (from the sealed end) a sufficient distance from the base's inner, bottom wall in order to provide protection thereof. Maintenance of this distance is assured by cementing the bulb (along the outer walls) to the base. It is also necessary in this design to pass the lamp's projecting lead-in wires through corresponding passages (holes) within the base, thus mandating a relatively complex (and time-consuming) alignment and insertion procedure. Even further, final lead-in wire retention necessitates yet another production step (e.g., heat staking) which adds still further to the cost of this lamp.
In the aforementioned U.S. Pat. No. 4,630,278, there is defined an electric lamp and base assembly wherein many of the several problems inherent in such prior art designs are overcome. Specifically, the assembly defined therein utilizes a base member wherein projecting ends of the assembly's lead-in conductors (wires) are oriented in spaced orientation along the opposing sides of the base and inserted within corresponding, similarly shaped apertures also within the base. In effect, a friction fit between the base and each wire is provided. On occasion, it has been determined that such a retention may prove insufficient to completely maintain the conductors in the desired fixed orientation. That is, on some occasions (e.g., wherein high tension forces were applied to both lamp envelope and base), the terminal ends of the conductors have become withdrawn from their respective base apertures.
The instant invention overcomes this undesirable feature by providing enhanced conductor retention within the base and, in addition thereto, means for providing additional restraint on the sealed end of the lamp within the base's socket. Such an invention is deemed to constitute a significant advancement in the art.